The presently disclosed subject matter relates to a biological signal averaging processing device which subjects a biological signal formed by repeatedly appearing analogous waves to a summing-averaging processing to thereby remove random noise therefrom. In the present specification, noise means a signal other than a required biological signal and includes an unnecessary biological signal as well as disturbance noise.
A signal-averaged electrocardiogram test may be performed in order to predict cardiac sudden death. A patient, who likely dies suddenly due to cardiac cause, is apt to generate a delayed minute potential (late ventricular potential (LP: late potential)) at the end portion of a QRS wave in an electrocardiogram. Conventionally, the signal-averaged electrocardiogram test has been performed in order to detect the LP. JP-A-2002-224068 discloses a method of detecting the LP. According to this literature, an XYZ lead electrocardiogram led from electrodes connected to a patient's body is converted into time-series digital data, and then subjected to the summing-averaging processing in synchronism with R-wave positions to thereby detect the LP.
The summing-averaging processing is performed in order to detect a minute LP accurately by removing the influence of noise (random noise).
A non-patent document 1 discloses a cerebral evoked potentiometer which detects, mainly from the scalp, changes of minute potentials led to respective sensory areas of a cerebrum in response to a stimulation to visual sense, auditory sense and somatic sense etc., in order to detect various kinds of abnormalities of a central nervous system due to cerebral tumor, cerebral infarction etc., and functional abnormality of sensory pathways to the respective sensory areas of the cerebrum via a brain stem from various kinds of sensory receptors of periphery, for example.
The minute potentials thus led contain a visual evoked potential (VEP) led by a stimulation of flash and pattern light, a somatosensory evoked potential (SEP) obtained by electrically stimulating a sensory nerve of periphery, a long-latency auditory evoked potential (AEP) led by a stimulation of tone burst or click and an auditory brainstem response (ABR) etc. These potentials are minute potentials almost in a range from 0.1 to 10 μV buried within an electroencephalographic signal.
The electroencephalographic signal containing the evoked potentials is subjected to an analog-to-digital conversion and subjected to the summing-averaging processing in synchronism with stimulations, whereby the evoked potentials buried within noise, that is, electroencephalogram can be detected. As potentials for obtaining a required biological signal by removing the random noise through the summing-averaging processing, there are the somatosensory evoked potential (SEP), a brainstem auditory evoked potential (BAEP), the visual evoked potential (VEP) and various kinds of event related potentials (ERP), for example.